U.S. patent application number 10/017526 was filed with the patent office on 2002-11-28 for calibrated power amplifier module.
This patent application is currently assigned to Analog Devices, Inc.. Invention is credited to McMorrow , Robert J..
Application Number | 20020175751 10/017526 |
Document ID | / |
Family ID | 26689990 |
Filed Date | 2002-11-28 |
United States Patent
Application |
20020175751 |
Kind Code |
A1 |
McMorrow , Robert J. |
November 28, 2002 |
Calibrated power amplifier module
Abstract
A power amplifier module includes an input for receiving a
signal having an input power level, at least one power amplifier
coupled to the input to increase the input power level of the
signal to an output power level and a power calibration and control
module coupled to the power amplifier for measuring the output
power level and correcting the output power level measurement based
on a set of factors. The power calibration and control module
further controls the at least one power amplifier to produce an
output power level equivalent to a target power level. The power
calibration and control module may include a power detector, a
power calibrator and a power controller. The power amplifier module
may further include a power set interface coupled to the power
calibration and control module for providing the target power
level.
Inventors: |
McMorrow , Robert J.; (
Concord, MA) |
Correspondence
Address: |
Jean
Tibbetts
Bromberg & Sunstein LLP
125 Summer Street
Boston
MA
02110
US
jtibbetts@bromsun.com
617-443-9292
617-443-0004
|
Assignee: |
Analog Devices, Inc.
One Technology Way
Norwood
02062
MA
|
Family ID: |
26689990 |
Appl. No.: |
10/017526 |
Filed: |
December 14, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60/292,782 |
Oct 52, 200 |
|
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Current U.S.
Class: |
330/129 |
Current CPC
Class: |
H03G 3/3042
20130101 |
Class at
Publication: |
330/129 |
International
Class: |
H03G 003/20 |
Claims
Claims
1. A power amplifier module comprising:a. an input for receiving a
signal having an input power level;b. at least one power amplifier
coupled to the input to increase the input power level of the
signal to an output power level;c. a power detector in signal
communication with the power amplifier to measure the output power
level;d. a power controller for comparing the output power level to
a target power level and producing a control signal for the power
amplifier based on the comparison; ande. a power calibrator coupled
to the power controller for determining a correction based on a set
of factors.
2. A power amplifier module according to claim 1, wherein the power
calibrator adjusts the target power level based on the
correction.
3. A power amplifier module according to claim 1, wherein the power
calibrator adjusts the measured output power level provided by the
power detector based on the correction.
4. A power amplifier module according to claim 1, wherein the power
calibrator adjusts the control signal produced by the power
controller based on the correction.
5. A power amplifier module according to claim 1 further including
a power set interface coupled to the power detector for providing
the target power level.
6. A power amplifier module according to claim 1, further including
at least one power sampling element coupled to the at least one
power amplifier and the power detector for sampling a portion of
the output power level and delivering the sampled output power to
the power detector.
7. A power amplifier module according to claim 1, wherein the power
detector is a logarithmic amplifier.
8. A power amplifier module according to claim 1, wherein the power
calibrator includes a set of laser trimmed resistors.
9. A power amplifier module according to claim 1, further including
a set of calibration pins coupled to the power calibrator for
receiving a voltage to program at least one of the set of
factors.
10. A power amplifier module according to claim 1, wherein at least
one of the set of factors is programmed digitally in the power
calibrator.
11. A power amplifier module according to claim 5, wherein the
power set interface is a digital interface.
12. A power amplifier module according to claim 5, wherein the
power set interface is an analog interface.
13. A power amplifier module according to claim 1, wherein the at
least one power amplifier, the power detector, the power controller
and the power calibrator are implemented on a single semiconductor
die.
14. A power amplifier module according to claim 1, further
including RF matching elements.
15. A power amplifier module according to claim 1, further
including RF switches.
16. A power amplifier module according to claim 1, wherein the
power set interface provides a controlled power burst.
17. A power amplifier module comprising:a. an input for receiving a
signal with an input power level;b. at least one power amplifier
coupled to the input for increasing the input power level of the
signal to an output power level;c. means for measuring the output
power level coupled to the power amplifier;d. means for comparing
the measured output power level to a target power level and
producing a control signal;e. means for adjusting at least one of
the measured output power level, the target power level and the
control signal using a correction based on a set of factors.
18. A power amplifier module according to claim 17, further
including a power set interface for providing the target power
level.
19. A power amplifier module according to claim 17, further
including means for sampling the output power level from the at
least one power amplifier.
20. A power amplifier module according to claim 17, further
including a set of calibration pins coupled to the means for
adjusting for receiving a voltage to program at least one of the
set of factors.
21. A power amplifier module according to claim 17, wherein at
least one of the set of factors is programmed digitally in the
power calibrator.
22. A power amplifier module according to claim 18, wherein the
power set interface is a digital interface.
23. A power amplifier module according to claim 18, wherein the
power set interface is an analog interface.
24. A power amplifier module comprising:a. an input for receiving a
signal having an input power level;b. at least one power amplifier
coupled to the input to increase the input power level of the
signal to an output power level; andc. a power calibration and
control module coupled to the power amplifier for measuring the
output power level and correcting the output power level
measurement based on a set of factors.
25. A power amplifier module according to claim 24, wherein the
power calibration and control module controls the at least one
power amplifier to produce an output power level equivalent to a
target power level.
26. A power amplifier module according to claim 25, further
including a power set interface coupled to the power calibration
and control module for providing the target power level.
27. A power amplifier module according to claim 24, further
including at least one power sampling element coupled to the at
least one power amplifier for sampling a portion of the output
power level of the signal and delivering the sampled output power
level to the power calibration and control module.
28. A power amplifier module according to claim 26, wherein the
power set interface is a digital interface.
29. A power amplifier module according to claim 26, wherein the
power set interface is an analog interface.
Description
Cross Reference to Related Applications
[0001] This application claims priority from United States
provisional patent application serial number 60/292,782, filed May
22, 2001, entitled "Calibrated Power Amplifier Module" and bearing
attorney docket number 2550/104, the disclosure of which is
incorporated herein, in its entirety, by reference.
Background of Invention
[0002] FIELD OF THE INVENTION
[0003] The invention relates generally to power amplifiers and,
more particularly, to power measurement and control in a power
amplifier.
[0004] BACKGROUND OF THE INVENTION
[0005] Power amplifiers (PAs) may be used in a variety of
applications to increase the power level of a signal. For example,
a power amplifier may be used as the final gain stage in the
transmitter of a mobile handset terminal (e.g., a mobile phone).
Typically, power measurement and control is required to ensure
compliance with regulations imposed on RF emissions and output
power. It is also desirable to minimize power consumption by
operating at the lowest possible output power levels. The power
measurement and control performed at a final test stage of a mobile
handset device generally requires a calibration step to program
correction coefficients into the mobile handset to compensate for
measurement errors. This can be a time consuming and costly process
that is generally performed on every mobile handset manufactured by
a vendor. In addition, this is a redundant measurement as the
manufacturer of the power amplifier also measures the output power
of each power amplifier to ensure compliance with
specifications.
[0006] Figure 1 is a schematic block diagram of an exemplary GSM
(Global System for Mobile communication) transmitter for a mobile
handset terminal. A power amplifier module (PAM) 102, coupler 114
and power detector 118 are used to create closed loop power
control. Power amplifier module 102 includes a power amplifier
integrated circuit 104 and a power controller integrated circuit
106. The power amplifier module 102 may also include RF matching
elements 108, filters 110 and RF switches 112. Power amplifier
module 102 is used to adjust the input power level of an RF signal
to a required power level and deliver the RF signal with an output
power level to an antenna 116 load.
[0007] To control the output power level of the RF signal, a
coupler 114 samples the output power level of the signal and sends
the sample to a power detector 118. The power detector 118 may be,
for example, a logarithmic amplifier. The sampled output power is
measured by the power detector 118 and the measured power is
delivered to the power controller 106. Power controller 106
compares the measured power to a power set voltage 120 (i.e., a
voltage level corresponding to the desired power level) input to
the power controller 106. The manufacturer of the mobile handset
terminal must provide a power set voltage 120 that has been
corrected (or calibrated) for error caused by various factors such
as temperature variation, detector variation with power level and
filter/coupler loss variations. A manufacturer may, for example,
apply an algorithm to adjust the power set voltage 120 for the
average non-linearity of the detector. These calibration
corrections are then stored in memory in the mobile handset
terminal.
[0008] The power controller 106 then controls the power amplifier
104 based on the comparison of the measured output power to the
power set voltage so that the output power level of the power
amplifier matches the desired power level. Generally, a
manufacturer of a mobile handset will measure the power of each
hand set after assembly and program the correction factors into the
handset memory. As mentioned above, this can be a costly and
time-consuming process. In addition, the process is redundant since
each PAM 102 itself must be measured against power
specifications.
Summary of Invention
[0009] In accordance with one aspect of the invention, a power
amplifier module includes an input for receiving a signal having an
input power level, at least one power amplifier to increase the
input power level of the signal to an output power level, a power
detector to measure the output power level, a power controller for
comparing the output power level to a target power level and
producing a control signal for the power amplifier based on the
comparison and a power calibrator for determining a correction
based on a set of factors. A power set interface may be coupled to
the power controller to provide the target power level. The power
amplifier module may further include a power sampling element for
sampling a portion of the output power level and delivering the
sampled output power to the power detector.
[0010] In one embodiment, the power calibrator adjusts the target
power level based on the correction. Alternatively, the power
calibrator may adjust the measured output power level provided by
the power detector or the control signal produced by the power
controller.
[0011] In another embodiment, the power detector is a logarithmic
amplifier. The power calibrator may include a set of laser trimmed
resistors. In a further embodiment, the power amplifier module
further includes a set of calibration pins coupled to the power
calibrator for receiving a voltage to program at least one of the
set of factors. Alternatively, the set of factors may be digitally
programmable. The power set interface may be a digital or analog
interface. In yet another embodiment, the power amplifier, the
power detector, the power controller and the power calibrator are
implemented on a single semiconductor die. The power amplifier
module may further include RF matching elements or RF switches. The
power set interface may provide a controlled power burst for GSM
and EDGE signals.
[0012] In accordance with another aspect of the invention, a power
amplifier module includes an input for receiving a signal with an
input power level, at least one power amplifier for increasing the
input power level of the signal to an output power level and means
for measuring the output power level. The power amplifier module
also includes means for comparing the measured output power level
to a target power level and producing a control signal and means
for adjusting at least one of the measured output power level, the
target power level and the control signal using a correction based
on a set of factors.
[0013] In one embodiment, the power amplifier module further
includes a power set interface for providing the target power
level. In another embodiment, the power amplifier module further
includes means for sampling the output power level from the at
least one power amplifier. A set of calibration pins may be coupled
to the means for adjusting to receive a voltage to program at least
one of the set of factors. Alternatively, the set of factors may be
digitally programmable. The power set interface may be a digital or
analog interface.
[0014] In accordance with another aspect of the invention, a power
amplifier module includes an input for receiving a signal having an
input power level, at least one power amplifier to increase the
input power level of the signal to an output power level. The power
amplifier module further includes a power calibration and control
module for measuring the output power level and correcting the
output power level measurement based on a set of factors. The power
calibration and control module may also control the at least one
power amplifier to produce an output power level equivalent to a
target power level.
[0015] In one embodiment, the power amplifier module further
includes a power set interface coupled to the power calibration and
control module for providing the target power level. The power set
interface may be a digital interface or an analog interface. In
another embodiment, the power amplifier module includes at least
one power sampling element coupled to the at least one power
amplifier and the power detector for sampling a portion of the
output power level of the signal and delivering the sampled output
power level to the power calibration and control module.
Brief Description of Drawings
[0016] The foregoing and advantages of the invention will be
appreciated more fully from the following further description
thereof with reference to the accompanying drawings wherein:
[0017] Figure 1 is a schematic block diagram of an exemplary GSM
transmitter for a mobile handset device.
[0018] Figure 2a is a schematic block diagram of a calibrated power
amplifier module in accordance with an embodiment of the present
invention.
[0019] Figure 2b is a schematic block diagram of a calibrated power
amplifier module in accordance with an alternative embodiment of
the invention.
[0020] Figure 2c is schematic block diagram of a calibrated power
amplifier module in accordance with an alternative embodiment of
the invention.
[0021] Figure 3 is a schematic block diagram of a calibrated power
amplifier module in accordance with an alternative embodiment of
the present invention.
Detailed Description
[0022] In an embodiment of the invention, a power amplifier module
(PAM) includes calibration and power control functions to correct a
measured output power of the PAM and to adjust the output power of
the PAM to match a desired power level over temperature and dynamic
power level ranges. The calibration function is incorporated into a
final test routine of the PAM by adding calibration circuitry to
the PAM. The calibration circuitry advantageously provides one-time
programmable corrections to the output power level of the PAM
before the PAM is incorporated into an application, such as a
mobile handset terminal. While embodiments of the invention will be
described generally with reference to mobile handset terminals, it
is to be understood that many signal transmission applications may
similarly benefit from various embodiments and improvements that
are subjects of the present invention.
[0023] Figure 2a is a schematic block diagram of a calibrated power
amplifier module in accordance with an embodiment of the invention.
Power amplifier module 202 includes at least one power amplifier
integrated circuit 204 to boost the input power level of an RF
signal to the required power level. The power amplifier 204 may be,
for example, a Gallium Arsenide (GaAs) or Silicon power amplifier
integrated circuit. The RF signal with an output power level
(P.sub.out_PAM) is delivered from PAM 202 to an antenna 216
load.
[0024] PAM 202 also advantageously includes an integrated power
control loop that includes a coupler 214 and a power control and
calibration unit 226 to control and correct the output power of the
RF signal and to adjust the output power to match the required
power level. Coupler 214 is used to sample a portion of the output
power level (P.sub.out_PAM) of the RF signal and send it to the
power control and calibration unit 226. Coupler 214 may be any
coupler generally known in the art. In one embodiment, coupler 214
may be a directive coupler such as that described in further detail
in co-pending U.S. patent application serial no. 10/016,976, filed
on even date herewith, entitled "Active Coupler," attorney docket
number 2550/113.
[0025] The power control and calibration unit 226 is used to
measure and correct the output power to compensate for errors in
the power measurement due to various system variables. In addition,
the power control and calibration unit 226 controls the output
power level (P.sub.out_PAM) produced by the power amplifier 204 so
it will match a desired power level. Power control and calibration
unit 226 includes a power detector 218, calibration circuitry 222,
and a power controller integrated circuit 206. Power detector 218
receives the sampled output power of the RF signal from the coupler
214. The power detector 218 may be, for example, a logarithmic
amplifier, detector diodes or an RMS power detector. Power detector
218 measures the sampled output power and delivers a reference
voltage proportional to the output power to the power controller
206. The power controller 206 compares the required power level to
the measured output power and based on this comparison produces an
appropriate control signal to control the power amplifier.
[0026] The required power level is set using a power set voltage
220 input to the power controller 206. The power set voltage may
first pass through the calibration circuitry as shown in Figure 2a.
Either an analog or digital power set interface may be used to set
the required power level. In the case of an analog power set
interface, the power set voltage is the true power set point in
dBm/volt, for a digital power set interface, the power set voltage
is the true power set point in dBm/bit. The power set interface is
used to determine the required power level based on factors such as
where a user is located, transmission standards, etc. In addition,
the power set interface may include elements to provide a
controlled power burst required for GSM and EDGE (Enhanced Data GSM
Environment) signals.
[0027] Once the power set voltage 220 has been provided to define
the required power level (P.sub.set), the power controller 206
compares the measured output power (P.sub.detector) of the signal
to the required power (P.sub.set). The comparison value,
P.sub.detector vs. P.sub.set, is then used to provide an
appropriate control signal to the power amplifier to adjust the
output of PAM 202 to match the required power level. In addition,
calibration circuitry 222 is used to calculate any correction (or
adjustment) needed to compensate for errors in the power
measurements caused by various factors such as temperature
variations, frequency variations, detector variation with power
level or filter/coupler loss variations. The addition of these
corrections should produce an exact relationship between the actual
output power from the PAM and V.sub.set.
[0028] Without calibration circuitry 222, the actual output power
of PAM 202 would deviate from the required power level due to
errors from, for example, detector 218 and coupler 214 due to the
factors mentioned above. The calibration circuitry 222 may be used
to adjust various values such as the power set voltage (V.sub.set),
the measured output power (P.sub.detector), the control signal
(V.sub.control) produced by the power controller 206 or any
combination of these values. Figure 2a shows calibration circuitry
222 used to correct the power set voltage V.sub.set 222. Figure 2b
shows an alternative embodiment of a calibrated PAM 202 in which
V.sub.set and P.sub.detector are corrected using calibration
circuitry 222. Figure 2c shows a further embodiment of a calibrated
PAM 202 in which V.sub.set , P.sub.detector and the control signal
V.sub.control are corrected using calibration circuitry 222. As
mentioned, any combination of these values may also be corrected
using calibration circuitry 222.
[0029] Returning to Figure 2a, the calibration circuitry may
perform a mathematical function that includes a number of
predetermined calibration (or correction) coefficients for the PAM.
There are many known correction or calibration formulas known in
the art that may be used. The calibration coefficients are based on
the PAM's behavior in various conditions (e.g., over a given
temperature or power level range). In one embodiment, the
calibration coefficients for the PAM may be determined by measuring
the power set voltage 220 required to produce each required power
level in a range of required power levels over ranges of frequency,
temperature, voltage or other system variable. These measurements
determine the errors between the actual power produced by PAM 202
and the power set voltage (V.sub.set). These errors provide an
indication of which direction V.sub.set (or P.sub.detector or
V.sub.control or a combination thereof) needs to be adjusted to
eliminate the errors.
[0030] In an alternative embodiment, the calibration coefficients
are determined by measuring a small subset of power set voltages
required to produce a subset of the required power levels over a
subset of frequencies, temperatures, etc. Known trends about the
variation in output power versus the power set voltage and the
various system variables (e.g., temperature, frequency, etc.) may
then be applied to compute the calibration coefficients.
[0031] Once the calibration coefficients are determined, they are
programmed into the calibration circuitry 222. In one embodiment,
the calibration circuitry consists of laser trimmed resistors. An
analog voltage may be used to burn in calibration (or correction)
coefficient(s) in the calibration circuitry 222. Alternatively, the
calibration circuitry 222 may be programmed digitally with the
calibration (or correction) coefficient(s). A calibration pin (or
pins) may be used as the calibration input 224 to input voltages to
program the calibration coefficients used to determine a correction
as described above. The voltages may be used to open resistor or
diode ladder networks.
[0032] As mentioned above, the calibration circuitry 222 is used to
calculate any correction or adjustment for the power measurements
to compensate for measurement errors due to variations in a number
of system variables. In one embodiment, as shown in Figure 2a, the
calibration circuitry corrects the measured output power for a
given power set voltage (V.sub.set) 220 by modifying the power set
voltage such that V.sub.set' = f (V.sub.set). The corrected power
set voltage, V.sub.set' , is then sent to the power controller 206
to be used to produce a desired power level (P.sub.set) that is
then compared against the measured output power (P.sub.detector).
The function, f, of the calibration circuitry 222 may be designed
so that V.sub.set' has the inverse of the errors present at the
measured output power. Thus, the errors will cancel and the power
controller will deliver a control voltage (V.sub.control) signal to
the power amplifier 204 necessary to produce the desired output
power. As mentioned above, in various other embodiments (as shown
for example, in Figs. 2b and 2c), the calibration circuitry may be
used to perform similar functions on the measured output power
(P.sub.detector), the control signal (V.sub.control) or some
combination of V.sub.set, P.sub.detector and V.sub.control.
[0033] Accordingly, PAM 202 in Figure 2a advantageously includes
power detection, calibration and control functions so that the
output power of a signal may be corrected and adjusted to match an
analog or digital power set point over a range of temperatures,
dynamic output powers etc., before being incorporated into an
application such as a mobile handset. In one embodiment, the power
amplifier, power detector, power control and calibration functions
are all included on a single semiconductor die.
[0034] In another embodiment, the power amplifier module may
include additional functions as shown in Figure 3. The power
amplifier module 302 may also include RF matching elements 326 such
as ceramic capacitors and inductors. In addition, filters 326 and
RF switches 326 may be included in the PAM 202.
[0035] Although various exemplary embodiments of the invention have
been disclosed, it should be apparent to those skilled in the art
that various changes and modifications can be made that will
achieve some of the advantages of the invention without departing
from the true scope of the invention. These and other obvious
modifications are intended to be covered by the appended
claims.
* * * * *